I send photons one at a time through a Mach–Zehnder interferometer with two detectors. Quantum superposition ensures that photons only reach one of the detectors.
The interferometer is initially built on a frame. However, I can adjust it to allow the half-silvered mirrors to no longer be attached to each other by the frame, but move freely.
I perform the experiment with a single photon. One hour later, I measure the position of each mirror to determine if it was struck by the photon.
Does this minor change to the apparatus ensure that the superposition disappears and photons arrive at both detectors with equal probability?